Method and apparatus for heat-treating



Aug. 20, 1963 c. e. BARKLEY ETAL 3,101,155

' METHOD AND APPARATUS FOR HEAT-TREATING Filed May 13. 1960 6 Sheets-Sheet 1 INVENTORS CHARLES G. BARKLEY JOHN BEESLEY ATTORN Aug. 20, 1963 c. G. BARKLEY ETAL 3,101,165

METHOD AND APPARATUS FOR HEAT-TREATING Filed May 15, 1960 s Sheets-Sheet 2 INVENTORS CHARLES G. BARKLEY JOHN R. BEESL EV ATTORNEYS Aug. 20, 1963 c. s. BARKLEY ETAL 3,101,155

METHOD AND-APPARATUS'FOR HEAT-TREATING Filed May 13, 1960 6 Sheets-Sheet 3 "'INVENIORS 3; 'CHARL 5 '6. BARKLEY JOHN RBEESLEY ATTOR/V 1 1963, c. G. BARKLEY ETAL 3,101,165

METHOD AND APPARATUS FOR HEAT-TREATING mvENToRs v CHARLES 6 BARKLEY JOHNR. BEESLEY A TTORNE Y Aug. 20, 1963 c. G. BARKLEY AETAL 3,101,155

METHOD AND APPARATUS FOR HEAT-TREATING Filed May 15, 1960 s Sheets-Sheet 5 INVENTORS CHARLES G. BARKLEY JOHN R. BEESLEY BY flw, 7

ATTOR EYS Aug. 20, 1963 c. G. BARKLEY ETAL 3,101,165

- METHOD AND APPARATUS FOR HEAT-TREATING Filed May 13., 1960 S SheetS-Sheet s TIE-1.2 RE-.12

INQVENTOYRS CHARLES c. BARKLEY JOHN R. BEESLEY ATT RNEYS 3,101,165 METHGD AND APPARATEE FUR I HEAT-TREATING I Charles G. Barkley and John R. Beesley, Foster-la, Ghio, assiguors to Atlas Crankshaft Corporation, Columbus, Ind a corporation of Indiana I Filed May 13, 196i Ser. No. 23,913

4 Claims. (Cl. 266-4) l v This invention relates to the heat treatment of metals and more particularly to the heat treatment of elongate metallic articles. I l I In the manufacture of certain elongate steel articles such as crankshafts, it is frequently necessary to increase the hardness of selected areas, such as the axially aligned main bearings and the radially offset connecting rod bearings, for the .purpose of providing adurable and wear resistant surface. To accomplish this, theselecteda'rea of the article is subjected to a heat treating operation in which heat is applied to the area for a prescribed length of time; the heat is shut oil; and a quenching solution is applied to the selected area to rapidly cool it and effect the necessary hardening. p

Inperforming such a heat treating operation it is becoming increasingly important that the time consumed in heat treating be reduced'and that the quality be increased.

This invention discloses amethod and apparatus which improves the speed and quality of such heat treating. it utilizes a pair of carriages which are movable in relation to each otheruand alsowith respect to an improved heat treating means. One of the carriages supports the article to be treatedfand moves it into position for heat treating.

In this invention the means for heat treating includes means for heating theselected area and integralmeans for applying a quenching solution to the selected area and is further: constructed to permit pivotal separation of certain hldhlfid Patented Aug. 20, 1563 2 FIGURE 5 is a section taken along line 55 of FIGURE 1; FIGURE 6 is a view, partially cut away, taken along line 6-6 of FIGURE 1 with the crankshaft A removed;

FIGURE 7 is'a section along line 77 of FIGURE 2; FIGURE 8 is a section taken along fines -8 of FIGURE 6; and FIGURE 9 is a view taken from line 9-9'0f FIG- URE 6. t

Infthe drawings, 1 designates a rectangularly shaped tank which holds the quenching solution utilized in the heat treating operation. It is comprised of a front sheet 3, a rear sheet Spend sheets (not shown) extending vertically upwardly from a bottom sheet 7, appropriately joined to each other as by welding. For the purpose of 29 iscentrally located with respect to the ends of the tank land also extends across the reinforcing members 13 and 15. It has two tapped holes to receive bolts 33 forthe purpose of centrallysupporting the tank particu larly in instances where the door on which the tank is located is not level throughout the length of the tank.

Locknut-s 35 hold the bolts in a selected position.

A lower carriage movable in a transverse directionis generally designated by All. For the purpose of support ing and guiding this lower carriage a front rail supporting 7 arrangement 4-2 is utilized that comprises a beam 41, a rail components thereof for positioning of the selectedarea within the confines of the heat treating means.

It is, therefore, an .object of this invention to provide an accurate and rapid means for positioning an elongate metallic article in relation to a heat treating means. it is a further object of this invention to provide a heattreating means that uniformly circumvents the selected area of the article during the heat treating operation and that is separable to permit rapid withdrawal of the articleupon the completion ofthe operation. In addition it is a goal of this invention to provide an arrangement wherein the article is supported on a firstcarriage for. movement to ward and away from a heat treating means and wherein salesmen and carriage are indexed longitudinally to position another selected area through movement of a second carriage supporting said first carriage. It is a fur: ther object of this invention to provide a method of heat treating elongate metallic articles whereby the article is supported for movement into position withrespect to a heat treating means which is relatively immobile. It is also an object of this invention to provide a means for pivotally separating a heat treating head to receive an artiole to be treated'and to provide a means for biasing the contacts of a pivotal member into firm engagement'with the contacts of a fixed member;

Other objects and advantages of this invention maybe its corners.

holdingiblock 429 having a recess at therein aflixed to the upper surface of the beam 41, and a carriage guiding rail 45 having a triangularly shaped upper section mounted in the recess 44 of the rail holding block 43. A rear rail supporting arrangement 48 is comprised of a beam 51 joined to the upper surface of the bottom plate 7 and disposed-above the member lS, a rail supporting block 53 joined to the upper surface of the beam 51, and a carriage tracking rail 55 mounted on the upper surface of the block As may best be as in FIGURES 3 and 5, the lower carriage all includes a platform 57 that has a pair of downwardly extending wheel supporting lugs59 near each of A wheel axle 63'extends through a hole 61 in each of the lugs 5% and is held in place by a nut 64 and alocking nut 66. For the purpose of properly guiding the carriage it} in its transverse movement, the wheels 65 located at the forward side of the platform 57 havea V- shaped peripheral groove 67 therein which mates with the upwardly extending triangularly shaped section of the rail 45. Rear wheels '81 have a flat cylindrical peripheral surface that contacts the upper surface of the carriage tracking rail 55; however, these Wheels primarily serve to support the carriage and do not serve the dual function of supporting and guiding as do the front wheels 65;v Each of the wheels1 65 and 81 is rotatably supported .by the axle 63 through intermediate bearing means, such as ball bearings 71 and 73 separated from each other bya spacer '75 and from the lugs 59 by spacers 77 and 79, In order,

seen. from the following description wherein-a preferred embodiment. of this invention as .l ltilized to heat treat selected a-reas of a crankshaft is clearly shown and from the following drawings wherein FIGURE l shows a front elevation partially cut away; FIGURE ZshoWs'a-Side elevation of this invention taken in thejdirection indicated by the arrow 2 of FIGURE 1; FIGURE 3 is a sectional viewtaken along line 33 of FIGURE 1; FIGUREAgis' a partial section taken along line'. i4' of FIGURE 1;.

to provide additional structural strength a transverse reinforcing'member, 87 having gussets83 and 85 extending I therefrom is utilized. j As an aid in maintaining accuracy and keeping the rails 45 free of metallic particles that might be Washed firom a crankshaft during a quenching operation, a scraping arrangement 92 is located at eachend of the platform 57 adjacent the wheels 65. It is comprised of a hanger 95, extending downwardly from the platform 57 above the rail .45, ac'over plate W joined to the hanger 95 by screws in a selected position by locknuts 106.

'A guiding arrangement 102 for an upper carriage 112 includes a track 107 afiixed to a pad 108 on the upper surface of the platform 57 and. extending perpendicular to the transverse center line of the platform. In order to properly limit the travel of the upper carriage112 toward the front and the rear of the tank 1, it is necessary to provide adjustable stops 1G9 and 111 respectively which .include. stop plates 11d joined to the platform 57 and screws 104 threadably engaging the plates 110 and held The upper carriage '112. includes a base 115, an termediate beam 117, a fixed supporting cradle 118 and a movable supporting cradle 119. The base 115 has a pair of central members 121 and 122 joined to the underside of a top plate 123, a pair of wheel supportinglugs .125 located at each corner of the top pla te123 and extending downwardly therefrom, wheels 1 26' mounted be tweenthe downwardly extending lugs on axles127 which serve aswheel bearings, transversely extending stop members 132 and 13-4 at the front and rear respectively, and a transversely extendingreinforcing member 136 extending from retainin'g'blook 13 1 to the lug 125. The wheels particles by scrapingarrangements 93.

' To prevent transverse movement of the upper carriage when it is moved toward the front and rear of the tank 1 on the; wheels 126, the guiding arrangement 102 includes retaining blocks 13-1 and 133 joined to the underside of the plate 123. These blocks have notches 135 and 137 cut in the lower portion thereof to receive wear plates 139 and: 141 held inplace by screws 143. Whenthe upper carriage 112 is positioned above the lower carriage 40-, these wear plates engage the track 107mounted on. the upper surface of the platform 57.

As best shown in FIGURE 4, pad 145 that has reamed holes 147 and tapped holes 149 therein is affixed to the top. surface of the'beam .117. These holes are situated to properly locate and retain outer guide'segments 152 and 154' and an intermediate segmentv 156 when locating dowels 157 are inserted into holes 147 and retaining screws 159 are engaged with the threaded holes 149;

In order to accurately adjust the cradle 119, the intermediate segment 15-6 is provided with a guideway 165 formed in its upper surface to receive a guide 167 joined to the bottom of the cradle 119. In addition the lower edges of the segment 156 are cut away as at 1 60- to cooperate with adjacent cut away portions designated 162 of the outer segments 152 and 154 to form a groove T-n-uts 164 slid'ably' mounted therein.

The adjustable cradle 119 includes a base 169 having a pin: receiving bushing 173 therein adapted to receive a locating'pin 175,, vertical guides 177 having slots 179 to receive a lower support block 18 1 and an adjustable upper V'-block 1'83, and reinforcing webs 185 connected I 126 move on flat rails 124 and are kept free of metallic I for t is reached, the pin 175 is inserted in the selected bushing' 163 and the screws 174- are tightened.

In order to adjust the upper block 183 a screw 184 is placed between block 183 and the lower block 1 81 with its threaded end engaging a tapped hole in the block 181 and its head engaging thelower side of block 183. Turning the screw into or out of the tapped hole lowers or raises the block 183. A locknut 1 8 9 locks the screw 184in any desired position.

A fixed cradle 118 is mounted on the pad'1 45 and is transversely disposed from the cradle 119. It includes a base 191, vertical guides 193 having grooves 195 joined to the base, a lower block 197, an upper adjustable,

V-block 1'98 and an adjusting screw (not shown) between the blocks. operable to adjust the vertical height in a fashion similar to the adjusting arrangement of the cradle 119. l 7

The upper carriage 11-2 receives a crankshaft on the adjustable V-blocks 183 and 198 and, in heat treating position, locates the crankshaft in close proximity to a heating coil and quenching head 210 that is adapted to V circumvent a connecting rod bearing or main bearing of the crankshaft. Through heat treating means, which will be hereinafter described, uniform heat is applied to the area selected for heat treating and at a, proper time in the cycle, it is cut off and a quenching solution is sprayed on the area. 1

This heat treating means includes the heating coil and quenching head 210, a high frequency current supplying transformer and electrical control unit 212 and an op: erator control means 216. The details of the lattertwo elements will not be specifically described since they are well known in the art. It should sufiice to state that the unit 212 be adapted to supply a high frequency current to the heating coil and quenching head 210 sufficient to heat the area to be heat treated. This, unit 212 is shown on the drawings in block form and:is adjustable in a vertical direction by screws 211 supporting the unit 212 on a platform 215. This affords a. means. for positioningthe head 210 dependent upon whether a main bearing is being heat treated in which case it is located toward the top of its travel or whether a connecting rod bearing, is being, heat treated in which case it is located toward, the bottom of its travel.

The electrical control. portion of the unit 212 establishes the proper timing cycle and the application of electrical current and quenching solution when the operator engages the controls means 216.

212' and physicallysup-ported by bolts 224 holding it to the bus bars 220 and 222. Thishead is of the double turn induction ring type and includes a stationary half.

226 and a movable half 228. As best seen in FIGURE 8, the-stationary half has. a quadrant 230 connected withthe bus bar 220, an adjacent quadrant 232, a quadrant 234. below the quadrant 232 and joined to the bus bar with the guides to provide rigidity. The locatingpin,

acting through-the bushing 173', engages bushings 163:

in the segment 156', thus accurately locating the cradle.

Screws 174extend through the base 169 and engage the T-nuts164'to secure the cradle in a selected'position when said screws. are tightened. Transverse adjustment T-nuts are guided along the cut outs between'the 'seg-- ments 156 and 152gand 154. When the clesiredposition 222, a quadrant :236 adjacent quadrant 234 and below quadrant 23.0, and a connector 238 electrically connecting quadrant 232 with quadrant 236. In order to physically join the adjacent. quadrants and to maintain electrical individuality, insulating brackets 240 and 242 made.

of nylon or a similar substance are bolted. tothe quadrants 230 and As shown inv FIGURE 9, the movable half 228 of the 232, and 234 and 236, respectively, by screws head is composed :of two. segments 250 and 252' which are physically joined by screws 253 extendingthrough lugs 254 and 2560f materials similar to the brackets 240 and 242.

The segments and quadrants serve the two purposes of conducting electrical current and channeling the quenching solution. To properly distribute therapplication of, heat, a recess 257 is provided in the internal peripheral" supported on selected main bearings. placed on the adjustable block 198 of the fixed cradle 11%, and a second main bearing is set on the adjustable block snor ss surface of the segments and quadrants, and to furnish an quenching solution deliveredto the passages 259 and 26%) through inlets similar'to inlet 261 located in each segment and'quadrant is supplied from the tank 1 by pump ing means (not shown). .It' is then taken from the passages 259 and 260' for application to a bearing portion 4 of a crankshaft through a plurality of holes 255. j

So that the movable half 228 may be pivoted to permit positioning of a crankshaft bearing between it and the stationary half 2% for heat treating and to insure a good electrical connection'at the contacts 258, a pivot bearing diameter of two inches. It a crankshaft having a main bearing diameter of two and one eighthinches is placed on the cradles 118 and 119, the longitudinal cenassembly, generally designated 265, and a latching arrangement 262 are utilized. The pivot assembly includes a bolt 267 having an en larged portion 263 with a hole 2m therein and having a threaded end 266. The enlarged end engages a slot fios 'in'the lug 256and receives a pivot pin 27Gabout which the movable half 228 pivots, and the threaded end 266 extends through an opening 272 in the bracket 242. A spring 274 fits around the bolt 267 and at one end engages the bracket 242 and at the other end contacts a washer 276 held in place by a tension-adjusting nut 278 in threadable engagement with the threaded end 266.

The latching arrangement 262 is comprised of a locking handle ass having a fiat surface 282and a cam surface 284-, a latching :member 286 pivotally support ing the locking handle by a'pivot pin 283, and a spring 2%. The latching member 286'has a flattened portion 292 that engages slots 294 and 296 in lug 254 and the bracketZdtt and a cylindrical portion 298 that extends through a hole in the bracket 240 andreceivesthe spring 290 at its outer end; Washers 3130 and 302. engage opposite ends of the spring and bear against the bracket '24!) and a'retaining' nut 304-. For the purpose of permitting release of the movable half 22% and longitudinal biasing movement of the latching member 236, a longitudinally extending slot 5% is provided in the flattened portion 292 of the latching member which receives a hinge pin 3%. A wear plate 1 31% is embedded in the'locking handle side ofthe lug 254- to prevent excessive wear when the cam 284 is moved to tension the latching arrangement. In performing a heattreating operation on an elongate metallic article, such as a crankshaft, an operator first moves the upper carriage .112 to what will be termed a work loading? 1 position. In this position (partially shown in broken lines on FIGURE 5), the upper carriage is disposed toward the front .stop i109 away from the rear stop 111 and the heatingcoil and quenching head are; wand the movable half 228 of the head isopen and ready to, receive a bearing of a crankshaft.

- ,fixture'so situated the operatorselects a crankshaft which With the holding may then be lifted by'an overhead crane hoist when the cnank-shaft is heavy or by manually pickingit up when it is of relatively light weight. in the 'case of a crankshaft which has main bearing portions axially aligned and an adjustment is, of course, also made to the adjusting means of the fixed cradle 118. The screw 134 is turned in the opposite direction to accommodate crankshafts of smaller diameters.

After placing the crankshaft in the properly adjusted cradles, the openator moves the upper carriage from the work loading position to what will be termed a heat treating position. To effect this movement the operator grasps the crankshaft or any other convenient. portion of the upper carriage 112 and exerts a force in the direction of the heating coil and quenching head 21%. The carriage moves rearwandly on the, wheels 126 moving along ra-ilsl124 and is guided by the wear plates 13% and 141 engaging the track 1617 until the stop member 132 engages the adjustable step 111 at the rear of the track 107. This stop limits the movement of the carriage toward the head 21% and is adjusted so thatthe'longitudinal center line of the crankshaft will coincide with the center of the head. When this position is reached the movable half 22,8 of the head is pivoted about the pivot pin 27%? v to a closed position wherein" the head-circumvents the a bearing to be treated. In closing, the movable half'ZZS pivots about pin 276 to a position where the contacts radially offset. connecting rod bearings, the crankshaft is One bearing is an adjusting means provides flexibility andpermits rapid v adaptation of the arrangement to crankshafts of difiterent main bearing diameters. v ture is adjusted to receive a crankshaft having a main As an example, assume the iix- 253 closest to the pivot pin 27a engage each other. When this position is reached, the operator then swing-s the latching member 2860f the latching arrangement 2&2 into the slots 2% and 2% of the lug 254 and the bracket 240 and the fiat surface 232; of the handie engages the wear plates are in the lug 254- of the movable half 228. Rotation of the locking handleZStt in a counter-clockwise direction, as shown in FIGURE 6, moves the cam surface 284- of the handle against the wear plate 310. This tends to pull the latching member to the left as viewed in FIG- URE6 against the force of spring 2%; simultaneously,

the spring 2% acts through the latching member and 'wear plate to move the contact-s 253 of the movable half 22% into engagement with the contacts 258 of the stationary half 226. Such movement also moves the bolt 26''] of the pivot assembly 265' to the left as viewed in'FlG- URE 6 against the tension of spring 274 holding the lower cont-acts 258 in firm engagement. Thus all contacts 258 are subjected to the force of springs 29% and 274 which establishes a good electrical contact.

With the movable half 223 closed, the operator then presses the electrical control means 216 to initiate the heat treating cycle. Electrical current is supplied to the head through bus bar 22% and carried through the head,

the latching arrangement 252, pivots the movable half 228 toan open position as shown in broken lines in FIG- URE 6, and pulls the upper carriage 11-2 longitudinally with respect to the head 21d toward a work leading position a sufficient distance to clear the crankshaft irom the head; A :force is then exerted on the lower carriage so in a transverse direct-ion, thus moving it along the rails 45 and 55 on wheels 65 and 81 and positioning the next hearing to be heat treated in alignment with the head ward movement toward the head and the above described cycle.

This cycle has been described with respect to the positioning and heat treating of a main hearing of a crank,

shaft; however, the procedure is similar with respect to a connecting rod hearing, except it is necessary to reposition the vertical height of either the head. 210 or the eradles 112 and 119 since the connecting rod hearing is radially ofiset from the longitudinal center line of the main hearings. This may he done by raising the crankshaft on the blocks 183 and 198 or lowering the head 2101a distance equal to the offset. The latter adjustment may be effected by turning the adjusting screw 211 supporting the transformer and control unit 212. Wi-th'the carriage 119 in a work loading position, the head in a loweredposition and the crankshaft main hearings supported on the blocks 183 and 198, the crankshaft connecting rod hearing to he treated is rota-ted downwardly below and vertically aligned with the longitudinal center line of the main hearings.- The carriage is then moved into 7 heat treating position against the rear stop 111 wherein the center line of the connecting rod hearing aligns itself vertically with the center of the head 210 which is in its lowered position; the movable half 228 is closed; and the operator then exerts a torceon the offset portion of the cranlsshafit toward the iront of the tank bringing the hearing into locating contact with a ceramic locating stop 316 adjustably secured in the segment 250 of the movable half. Such a locating stop is necessitated because of the tendency otthe connecting rod hearing to rotate about the main bearings. head a proper distance to locate the center line of the connecting rod hearing at the center of the head. To reduce the time consumed in changing from a set up adapted for treating main hearings. to a set up for treating connecting rod hearings, two arrangements utilizing this invention may be provided wherein main hearings are treated on one and connecting rod hearings on the other.

While a particular embodiment of invention has been shown, it will, or" course, he understood that the invention is not to be limited thereto, since many modifications to the arrangements disclosed may he made Without'departing from the spirit and scope thereof. It is of course contemplated that the appendi-ng claims cover any such. modifications as tall within the true spirit and scope of this invention.

'We claim:

1. Apparatus for heat treating a crankshaft having a plurality of main bearings and at least one connecting rod hearing, comprising a base, heat treating means mounted at the rear of the base and including a heating and quenching head projecting forwardly over the base, said head including a fixed half and movable half pivotally mounted on said fixed half and adapted to concentrically receive a connecting rod hearing therebetween,

'It is turned into the means for supporting a crankshaft comprising a lower carriage mounted on said base for movement parallel to the front of the base, an upper carriage mounted on said lower carriage for movement fonwardly and rearwardly of said base, supporting means mounted on said upper carriage tor rotatably supporting main hearings of the crankshaft, said upper carriage being movable rearwardly of the base to move a connecting rod hearing toward said head, said lower carriage having stop means for limiting the rearward movement of said upper carriage substantially to a position where a vertical plane through the axis'of themain hearings passes. through the center of said halves, and an insulating stop pin mounted in one of said halves and the crankshaft being adapted to he rotated in said supporting means to engage. the connecting rod bearing with said stop pin and thereby center the connecting rod hearing within said halves;

2. In an apparatus for heat treating the hearings of a crankshaft, a heating head comprising -a pair of members having semicircular recesses to receive a crankshaft hearing therebetween, said members including conductors forming said recesses, said conductors having contacts at their ends with the contacts on each of said members adapted .to engage the contacts on the other of said members, the conductors of one .of said members being adapted to be connected to a source oftelectrical energy, said members being resilient-1y connected to each other at each of their ends to hold the contacts of the respective members in engagement under a predetermined pressure. 3. An apparatus according to claim 2, in which the resilient connection at each end of said members coinprises a rod secured adjacent one of its ends to one of said members and slida'hl'y mounted in the other of said members, and a spring mounted on the other end of the rod and hearing against said other member;

4. An apparatus according to claim 3, in which the rod of one of said resilient connections isjpivotal-ly secured to said one member, and the rod of the other resilient connection is releasably secured to said one memher, whereby said one member may he released tromthe other member at one end and swung away from said other member for insertion and removal of a crankshaft hear- Great Britain Sept. 5, 1951 

1. APPARATUS FOR HEAT TREATING A CRANKSHAFT HAVING A PLURALITY OF MAIN BEARINGS AND AT LEAST ONE CONNECTING ROD BEARING, COMPRISING A BASE, HEAT TREATING MEANS MOUNTED AT THE REAR OF THE BASE, AND INCLUDING A HEATING AND QUENCHING HEAD PROJECTING FORWARDLY OVER THE BASE, SAID HEAD INCLUDING A FIXED HALF AND MOVABLE HALF PIVOTALLY MOUNTED ON SAID FIXED HALF AND ADAPTED TO CONCENTRICALLY RECEIVE A CONNECTING ROD BEARING THEREBETWEEN MEANS FOR SUPPORTING A CRANKSHAFT COMPRISING A LOWER CARRIAGE MOUNTED ON SAID BASE FOR MOVEMENT PARALLEL TO THE FRONT OF THE BASE, AN UPPER CARRIAGE MOUNTED ON SAID LOWER CARRIAGE FOR MOVEMENT FORWARDLY AND REARWARDLY OF SAID BASE, SUPPORTING MEANS MOUNTED ON SAID UPPER CARRIAGE FOR ROTATABLY SUPPORTING MAIN BEARINGS OF THE CRANKSHAFT, SAID UPPER CARRIAGE BEING MOVABLE REARWARDLY OF THE BASE TO MOVE A CONNECTING ROD BEARING TOWARD SAID HEAD, SAID LOWER CARRIAGE HAVING STOP MEANS FOR LIMITING THE REARWARD MOVEMENT OF SAID UPPER CARRIAGE SUBSTANTIALLY TO A POSITION WHERE A VERTICAL PLANE THROUGH THEE AXIS OF THE MAIN BEARINGS PASSES THROUGH THE CENTER OF SAID HALVES, AND AN INSULATING STOP PIN MOUNTED IN ONE OF SAID HALVES AND THE CRANKSHAFT BEING ADAPTED TO BE ROTATED IN SAID SUPPORTING MEANS TO ENGAGE THE CONNECTING ROD BEARING WITH SAID STOP AND THEREBY CENTER THE CONNECTING ROD BEARING WITHIN SAID HALVES. 